1. Field of the Invention
This invention relates to pyrotechnic materials and, more particularly, to a method for safe handling or pyrotechnic materials during mixing, casting and dispensing operations.
2. Description of the Prior Art
Methods have been available in the prior art in which small batches of pyrotechnic materials are mixed together. The batches are kept small to minimize the safety hazard in the event of accidental ignition due to friction heat as the fine particles of the pyrotechnic materials are being tumbled to obtain a homogeneous blend. The blending is usually done dry because of requirements for maintaining moisture within the batch to very low levels. After mixing, the dry batch is usually manually dispensed into the charge containers or shipping containers by weight or by volume.
The dry mixing and tumble blending and manual dispensing are each extremely hazardous operations. Pyrotechnic materials are inherently very sensitive to ignition induced by relatively low temperatures that can be generated by nothing more than a friction of the particles of material rubbing against each other during the dry processing. Indeed, some of these dry pyrotechnic materials are recognized as being so sensitive that the preferred mixing technique involves performing the actual blending by vibration means after the constituent materials for the blend have been loaded in strictly regulated, limited quantities into the final containers. In this way, process handling and resultant process hazards from accidental ignition of the mix are minimized.
Many different methods have been employed in the attempts to solve the problems presented. Most have either presented new problems or only partially solved the problems presented or both. Most of these prior art methods have thus met special needs as presented by specific problems and have therefore served only specific purposes. These prior art methods, among other disadvantages, have caused unacceptable degradation of ignition properties, have formed active compounds with the original pyrotechnic materials, have been unreliable and unpredictable in operation and have been expensive, complicated and still hazardous to effectuate.
As an example of these prior art methods, U.S. Pat. No. 3,702,271 discloses a method wherein an explosive slurry comprised of an organic liquid hydrocarbon is mixed, allowed to settle for decanting of excess hydrocarbon, further agitated under vacuum to remove an azeotropic mixture of the hydrocarbon and water, and then cast under vacuum to still further ensure the removal of any remaining hydrocarbon or azeotrope. This patent is specifically related to a process for the removal of water from explosive or propellant ingredients after manufacture and therefore does not address specifically the problem of providing a slurry mixture for processing explosive mixtures to form a final dispensed product.
U.S. Pat. No. 976,211 discloses the use of a slurry to minimize explosion during incorporation of explosive ingredients. The slurry utilized is defined as a volatile hydrocarbon such as gasoline, kerosene or benzene. Although this slurry media was particularly useful in the mixing of the explosive materials available at the date of this patent, these materials are not particularly useful in mixing the much more sensitive explosive materials now available.
U.S Pat. No. 3,180,771 discloses a method of preparing a rocket monopropellant compound wherein Freon 13 is disclosed as useful as a solvent for processing of low temperature ammonia with concentrated ozone for a chemical reaction which forms ammonia ozonate and other related compounds as a precipitate. These compounds are specifically for usage in high specific impulse rocket monopropellants.
Other patents which describe various techniques for forming pyrotechnic mixtures are U.S. Pat. Nos. 503,587, 2,027,114, 2,213,255, 2,646,596, 2,973,257, 2,992,088, 3,173,817, 3,193,991, 3,296,043, 3,393,255, 3,774,496, and 3,897,237.
A process technique is needed, therefore, to provide for safe handling of pyrotechnics during the mixing, blending and dispensing of these materials. A significant step forward in the art would be realized by a process which provides for safe handling during any one of the process phases, i.e. either mixing, blending or dispensing, and in addition assure the integrity of the ignition qualities of the blend.